JP6108215B2 - Zoom lens, camera, and portable information terminal device - Google Patents

Description

  The present invention relates to a zoom lens suitable for an imaging device using a solid-state imaging device or the like, and a camera and a portable information terminal device using such a zoom lens.

In recent years, zoom lenses that can select various focal lengths as desired, such as a wide-angle state with a short focal length and a wide angle of view, or a telephoto state with a long focal length and a narrow angle of view. Cameras equipped with a lens having a variable focal length function as a photographing lens have become widespread. In particular, an object optical image formed by a photographing lens is taken as electronic information by a solid-state imaging device such as a CCD (charge coupled device) imaging device, and the photographing lens with a variable focal length in a digital camera used for recording, transmission, printing, etc. The spread of is very remarkable.
There are a wide variety of user needs for digital cameras having a photographing lens having this type of variable focal length function, and among them, the needs for higher image quality and smaller size are particularly high. Therefore, a zoom lens used as a photographing lens is also required to achieve both high performance and downsizing.
Here, in terms of miniaturization, it is first necessary to shorten the total lens length during use (distance from the object plane of the lens closest to the object side to the image plane on which the image sensor is arranged). It is also important to reduce the lens thickness to reduce the total length during storage. Furthermore, in terms of high performance, it is necessary to secure a resolving power corresponding to an image sensor with at least 10 to 20 million pixels over the entire zoom range.
In addition, there are many users who wish to widen the angle of view of the taking lens, and the half angle of view of the zoom lens on the wide angle end side (short focal end side) is preferably about 45 degrees.

Furthermore, a large aperture is desired, and it is desirable that the F number at the short focal end is 2.0 or less.
There are many types of zoom lenses suitable for the photographic lens in the digital camera, but there is a zoom lens having a negative refractive power in the first lens group as a small type with a wide angle.
In order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power are arranged, and the first lens group is arranged from the object side. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2007-249087) and Patent Document 2 are known as conventional examples of a zoom lens composed of a negative lens having a concave surface on the image side, a negative lens having a concave surface on the image side, a biconcave lens, and a positive lens. (Japanese Unexamined Patent Application Publication No. 2008-122875) and Japanese Unexamined Patent Application Publication No. 2008-040159 (Japanese Unexamined Patent Application Publication No. 2008-040159).

However, the zoom lenses described in Patent Document 1, Patent Document 2, and Patent Document 3 have a half angle of view at the short focus end of about 42 degrees, and cannot be said to be sufficiently wide. The number is not made F2.0 or less.
The present invention has been made in view of the above points, and the invention according to claim 1 is such that the half angle of view of the short focus end is 45 degrees or more and the angle of view of the short focus end is sufficiently wide. An object of the present invention is to provide a zoom lens having a resolving power corresponding to an image sensor having a number of 2.0 or less and a configuration number of about 11 and having a small size and 10 to 20 million pixels.

In order to achieve the above-described object, the zoom lens according to the present invention provides
In order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power are arranged from the short focal end. Along with zooming to the long focal end, the distance between the first lens group and the second lens group decreases and moves so that the distance between the second lens group and the third lens group changes. In the zoom lens, an aperture stop is disposed between the first lens group and the second lens group, and the first lens group has, in order from the object side, a negative lens L11 having a concave surface on the image side, and a concave surface on the image side. A negative lens L12, a biconcave lens L13, and a positive lens L14 having a convex surface on the object side, and the second lens group in order from the object side is a positive lens L21, a positive lens L22, and a negative lens. Lens L23, positive lens L24, and negative lens L25 , And characterized in that it constitutes a positive lens L26.

According to the zoom lens according to the present invention,
In order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power are arranged from the short focal end. Along with zooming to the long focal end, the distance between the first lens group and the second lens group decreases and moves so that the distance between the second lens group and the third lens group changes. In zoom lenses,
An aperture stop is disposed between the first lens group and the second lens group, and the first lens group has, in order from the object side, a negative lens L11 having a concave surface on the image side and a negative lens having a concave surface on the image side. L12, a biconcave lens L13, and a positive lens L14 having a convex surface on the object side are arranged, and the second lens group includes, in order from the object side, a positive lens L21, a positive lens L22, a negative lens L23, By comprising the positive lens L24, the negative lens L25, and the positive lens L26, the short focus end has an F number of 2.0 at a short focus end of a sufficiently wide field angle of 45 degrees or more. In the following, it is possible to provide a zoom lens having a resolving power corresponding to an imaging element having a small number of constituent elements of about 11 and having a size of 10 to 20 million pixels.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows typically the zoom locus | trajectory accompanying the structure of the optical system of the zoom lens and zooming in Example (Numerical example. The same hereafter) 1 which concerns on the 1st Embodiment of this invention, (a) FIG. 4 is a cross-sectional view along the optical axis at the short focal end (wide angle end), (b) at the intermediate focal length, and (c) at the long focal end (telephoto end). FIG. 3 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the short focal end (wide angle end) of the zoom lens according to Example 1 of the present invention shown in FIG. 1. FIG. 3 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the intermediate focal length of the zoom lens according to Example 1 of the present invention shown in FIG. 1. FIG. 3 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the long focal end (telephoto end) of the zoom lens according to Embodiment 1 of the present invention shown in FIG. 1. It is a figure which shows typically the structure of the optical system of the zoom lens in Example 2 which concerns on the 2nd Embodiment of this invention, and the zoom locus | trajectory accompanying zooming, (a) is a short focus end, (b) is an intermediate | middle. The focal length and (c) are cross-sectional views along the optical axis at each of the long focal ends. FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion aberration and coma aberration at the short focal point of the zoom lens according to Embodiment 2 of the present invention shown in FIG. 5. FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the intermediate focal length of the zoom lens according to Example 2 of the present invention shown in FIG. 5. FIG. 6 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the long focal end of the zoom lens according to Embodiment 2 of the present invention shown in FIG. 5. It is a figure which shows typically the structure of the optical system of the zoom lens in Example 3 which concerns on the 3rd Embodiment of this invention, and the zoom locus | trajectory accompanying zooming, (a) is a short focus end, (b) is an intermediate | middle. The focal length and (c) are cross-sectional views along the optical axis at each of the long focal ends. FIG. 10 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the short focal point of the zoom lens according to Example 3 illustrated in FIG. 9; FIG. 10 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the intermediate focal length of the zoom lens according to Example 3 illustrated in FIG. 9. FIG. 10 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the long focal end of the zoom lens according to Embodiment 3 of the present invention shown in FIG. 9; FIG. 10 is a diagram schematically showing a configuration of an optical system of a zoom lens and a zoom locus accompanying zooming in Example 4 according to the fourth embodiment of the present invention, where (a) is a short focal end, and (b) is an intermediate. The focal length and (c) are cross-sectional views along the optical axis at each of the long focal ends. FIG. 14 is an aberration curve diagram showing spherical aberration, astigmatism, distortion aberration and coma aberration at the short focal point of the zoom lens according to Example 4 shown in FIG. 13. FIG. 14 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the intermediate focal length of the zoom lens according to Example 4 illustrated in FIG. 13. FIG. 14 is an aberration curve diagram showing spherical aberration, astigmatism, distortion and coma aberration at the long focal end of the zoom lens according to Example 4 shown in FIG. 13; It is a perspective view which shows typically the external appearance structure seen from the object side of the digital camera as a camera which concerns on the 5th Embodiment of this invention. It is the perspective view which shows typically the external appearance structure which looked at the digital camera of FIG. 17 from the photographer side. It is a block diagram which shows the function structure of the digital camera of FIG. 17 and FIG.

Hereinafter, based on an embodiment of the present invention, a zoom lens, a camera, and a portable information terminal device according to the present invention will be described in detail with reference to the drawings.
Before describing specific examples, first, a fundamental embodiment of the present invention will be described.
In the present invention, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power are arranged in this order from the object side. In other words, in a zoom lens composed of three negative-positive-positive lens groups, the distance between the first lens group and the second lens group decreases with zooming from the short focal end to the long focal end, As the distance between the second lens group and the third lens group changes, the second lens group has a zooming action.
Since the first lens unit is separated from the aperture stop at the short focal end, the first lens unit becomes large, and it is difficult to correct off-axis aberrations in the first lens unit. It becomes even more important to optically correct the distortion at the short focal end. When the first lens group is composed of a negative lens-negative lens-positive lens that is often used, it is difficult to correct off-axis aberrations because of the large aperture and wide angle. Therefore, in the present invention, the negative lens L11 having a concave surface on the image side, the negative lens L12 having a concave surface on the image side, the biconcave lens L13, and the positive lens L14 having a convex surface on the object side are arranged in order from the object side.

Furthermore, when the negative lens L11 and the negative lens L12 have concave shapes on the image side and the negative lens L13 has a biconcave shape, various aberrations can be corrected in a balanced manner. By constructing a concave surface on the object side with the negative lens L13 in which the incident angle of the off-axis light beam at the short focus end is the most gradual, various aberrations in the entire zoom range are corrected and off-axis light beam at the short focus end is corrected. Can be corrected sufficiently.
In addition, since the aperture is large, the configuration of the second lens group that passes through a position where the axial marginal ray is high becomes important. Therefore, in the present invention, the second lens group G2 is composed of a positive lens L21, a positive lens L22, a negative lens L23, a positive lens L24, a negative lens L25, and a positive lens L26 in order from the object side. Corresponds to item 1).
In particular, when the positive lens L22, the negative lens L23, and the positive lens L24 are joined together, and the negative lens L25 and the positive lens L26 are joined together, the eccentricity in the cemented lens can be reduced, and the surface accuracy error of the lens surface. The influence of can be reduced. In particular, by providing a cemented surface, it is possible to sufficiently suppress lateral chromatic aberration, which is a problem with wide-angle lenses, and chromatic coma, which is a problem with large-diameter lenses. In addition, spherical aberration, coma and the like can be sufficiently corrected while having a large aperture.

In order to achieve higher performance, it is desirable to satisfy the following conditional expression (1).
That is, the focal length of the first lens group is f1, and the focal length of the entire optical system at the short focal end is fw.
Conditional formula (1) below:
−4.0 <f1 / fw <−3.0 (1)
Is preferably satisfied (corresponding to claim 2).
If it is equal to or greater than the upper limit value of the conditional expression (1), the focal length of the first lens group becomes too long, the zooming efficiency of the second lens group deteriorates, and it is difficult to correct aberrations in the entire zoom range. become. On the other hand, if it is less than or equal to the lower limit value of conditional expression (1), the focal length of the first lens group becomes too short, and it becomes difficult to correct off-axis aberrations in the first lens group.
In order to achieve higher performance, it is desirable to satisfy the following conditional expression (2).
That is, the focal length of the second lens group is f2, and the focal length of the entire optical system at the short focal end is fw.
Conditional formula (2) below:
3.0 <f2 / fw <5.0
Is preferably satisfied (corresponding to claim 3).

If the upper limit of conditional expression (2) is exceeded, the focal length of the second lens group becomes too long, the zooming efficiency of the second lens group deteriorates, and it becomes difficult to correct aberrations in the entire zoom range. Become. If it is less than or equal to the lower limit value of conditional expression (2), the focal length of the second lens group becomes too short, and it becomes difficult to correct off-axis aberrations in the second lens group.
In order to achieve higher performance, it is desirable to satisfy the following conditional expression (3).
That is, the focal length of the third lens group is f3, and the focal length of the entire optical system at the short focal end is fw.
Conditional expression (3) below:
6.0 <f3 / fw <16.0 (3)
Is preferably satisfied (corresponding to claim 4).
By satisfying the conditional expression (4), the third lens group sets the exit pupil position to an appropriate distance from the sensor so that light rays are incident at an appropriate angle with respect to the sensor.
The focusing is preferably performed by the third lens group. In addition, the third lens group is composed of one positive lens, whereby the focus group can be reduced in weight, leading to energy saving.
The positive lens of the third lens group preferably has a convex shape on the object side (corresponding to claim 5).

In order to achieve high performance while being small, it is desirable that the following conditional expression (4) is satisfied.
That is, the thickness of the first lens group on the optical axis is D1, and the focal length of the entire optical system at the short focal end is fw.
Conditional expression (4) below:
3.5 <D1 / fw <6.5 (4)
Is preferably satisfied (corresponding to claim 6).
If the value is equal to or greater than the upper limit value of conditional expression (4), the first lens group becomes too thick, the air interval for zooming becomes too short, and it becomes difficult to correct aberrations in the entire zoom range. On the other hand, if it is less than or equal to the lower limit value of conditional expression (4), the first lens group becomes too thin and it becomes difficult to correct off-axis aberrations in the first lens group.
More preferably, the following conditional expression (4) ′ is satisfied.
3.0 <D1 / fw <4.0 (4) ′
In order to achieve high performance while being small, it is desirable that the following conditional expression (5) is satisfied.

That is, the thickness on the optical axis of the second lens group is D2, and the focal length of the entire optical system at the short focal end is fw.
Conditional formula (5) below:
2.5 <D2 / fw <4.5 (5)
Is preferably satisfied (corresponding to claim 7).
If the value is equal to or greater than the upper limit value of conditional expression (5), the second lens group becomes too thick, the air interval for zooming becomes too short, and it becomes difficult to correct aberrations in the entire zoom range. On the other hand, if it is less than or equal to the lower limit value of conditional expression (5), the second lens group becomes too thin, and it becomes difficult to correct off-axis aberrations in the second lens group.
More preferably, the following conditional expression is satisfied.
2.0 <D2 / fw <4.0 (5) ′
In order to further reduce the size and performance, it is preferable that the following conditional expression (6) is satisfied.
The distance between the aperture stop and the second lens group at the short focus end is TLs2_w, and the distance between the first lens group and the aperture stop at the short focus end is TL1s_w.
Conditional formula (6) below:
0.10 <TLs2_w / TL1s_w <0.60 (6)
Is satisfied (corresponding to claim 8).

If it is equal to or less than the lower limit value of conditional expression (6), the distance between the first lens group and the aperture stop becomes large, and off-axis rays passing through the first lens group at the short focal point become too high, and the first It becomes difficult to correct off-axis aberrations in the lens group, and the first lens group becomes large. On the other hand, if it is equal to or greater than the upper limit value of the conditional expression (6), the distance between the second lens group and the aperture stop becomes large, and the off-axis ray passing through the second lens group at the short focal point becomes too high, It becomes difficult to correct aberrations in the second lens group, and the second lens group becomes large.
The focusing is preferably performed by the third lens group. In addition, the third lens group is composed of one positive lens, whereby the focus group can be reduced in weight, leading to energy saving. The positive lens of the third lens group preferably has a convex shape on the object side.
When it is necessary to reduce the amount of light reaching the image plane, the aperture stop may be reduced in diameter, but the amount of light is reduced by inserting an ND filter (a neutral density filter) or the like without greatly changing the diameter of the aperture stop. Like that. This is more preferable because it can prevent a decrease in resolving power due to a diffraction phenomenon.
On the other hand, in the fifth embodiment of the present invention, the zoom lens (including the zoom lenses according to the second to fourth embodiments) according to the first embodiment of the present invention described above is used as the imaging optical. It is a camera such as a so-called digital camera configured as a system (corresponding to claim 9).

Such a camera can have a small size and high image quality by including the zoom lens as described above as a photographing optical system.
Moreover, it can also comprise using the zoom lens as mentioned above as an imaging | photography optical system of the imaging | photography function part in what is called a portable information terminal device which has imaging functions, such as a camera function (corresponding to claim 10).
Such a portable information terminal device has a photographing function, and has a zoom lens as described above as a photographing optical system, so that the angle of view at the wide-angle end is sufficiently wide as 45 degrees or more. However, a zoom lens having a resolving power corresponding to an image sensor with 10 to 20 million pixels having a small F number at the short focus end of 2.0 or less and a small number of constituent elements of about 11 is taken by the camera function unit. A small and high-quality portable information terminal device used as an optical system can be provided. For this reason, the user can take a high-quality image with a portable information terminal device excellent in portability and transmit the image to the outside.
As described above, according to the first aspect of the present invention, the half angle of view at the short focus end is 45 degrees or more and the F number at the short focus end is 2.0 or less while the angle of view is sufficiently wide. Therefore, it is possible to provide a zoom lens that has a resolution that is small and has a resolution corresponding to an image sensor with 10 to 20 million pixels.

According to the invention of any one of claims 2 to 5, it is possible to provide a high-performance zoom lens in which each aberration is corrected more satisfactorily.
According to the invention of any one of claims 6 to 8, a small and high-performance zoom lens can be provided.
According to the ninth aspect of the present invention, although the half angle of view at the wide angle end is sufficiently wide as 45 degrees or more, the F number at the short focal end is 2.0 or less and the number of components is as small as about 11 sheets. A small and high-quality digital camera or the like using a zoom lens having a resolving power corresponding to an image sensor with a size of 10 to 20 million pixels as a photographing optical system can be provided. High-quality images can be taken with an excellent camera.
According to the tenth aspect of the present invention, although the half angle of view at the wide angle end is sufficiently wide as 45 degrees or more, the F number at the short focus end is 2.0 or less, and the number of components is as small as about 11. Since a small and high-quality portable information terminal device using a zoom lens having a resolving power corresponding to an image sensor with a size of 10 to 20 million pixels as a photographing optical system of a camera function unit can be provided. Can take a high-quality image with a portable information terminal device excellent in portability and transmit the image to the outside.

Next, specific examples based on the above-described embodiment of the present invention will be described in detail. Examples 1 to 4 described below are examples of specific configurations according to numerical examples (numerical examples) of the zoom lens according to the first to fourth embodiments of the present invention. . 1 to 4 are diagrams for explaining a zoom lens in Example 1 according to the first embodiment of the present invention. 5 to 8 are diagrams for explaining a zoom lens in Example 2 according to the second embodiment of the present invention. FIGS. 9-12 is for demonstrating the zoom lens in Example 3 which concerns on the 3rd Embodiment of this invention. FIGS. 13 to 16 are for explaining a zoom lens in Example 4 according to the fourth embodiment of the present invention.
In each of the zoom lenses of Examples 1 to 4, the first lens group having negative refractive power, the second lens group having positive refractive power, and the first lens having positive refractive power are sequentially arranged from the object side. The zoom lens has a so-called negative-positive-positive three-group configuration in which three lens groups are arranged.
In the zoom lenses according to the first to fourth embodiments, the optical element formed of a parallel plate disposed on the image plane side of the third lens group includes various optical filters such as an optical low-pass filter and an infrared cut filter. And a cover glass (seal glass) of a light-receiving image pickup device such as a CMOS (complementary metal oxide semiconductor) image sensor or a CCD (charge coupled device) image sensor. Here, an equivalent transparent parallel plate And FG, etc., are collectively referred to.

Moreover, the glass material of the optical glass used in each Example of Example 1- Example 4 is the optical glass type name of the product of OHARA Co., Ltd. (OHARA), HOYA Corporation (HOYA), and Hikari Glass Co., Ltd. (HIKARI). Is shown.
Aberrations in the zoom lenses of the first to fourth embodiments are sufficiently corrected, and can correspond to light receiving elements having 10 to 20 million pixels or more. . Example 1 is that the zoom lens is configured according to the first to fourth embodiments of the present invention, and a very good image performance can be secured while achieving a sufficiently small size. -It is clear from each Example of Example 4.
Although distortion aberration can be corrected electronically, the correction has an effect on image quality. For this reason, the present invention achieves high image quality by optically correcting distortion aberration sufficiently.

The meanings of symbols common to the first to fourth embodiments are as follows.
f: Focal length of the entire optical system F: F value (F number)
ω: Half angle of view (degrees)
R: radius of curvature (paraxial radius of curvature for aspheric surfaces)
D: surface interval Nd: refractive index [nu] d: Abbe number K: aspherical conic constant A _4: 4-order aspherical coefficients A _6: 6-order aspherical coefficients A _8: 8-order aspherical coefficients A _10: 10 Next aspherical coefficient The aspherical shape used here is that the reciprocal of the paraxial radius of curvature R (paraxial curvature) is C, the height from the optical axis is H, and the conic constant is K. A spherical coefficient is used, and X is defined as an aspheric amount in the optical axis direction, which is defined by the following equation (7), and a shape is specified by giving a paraxial radius of curvature, a conical constant, and an aspheric coefficient.

FIG. 1 shows the lens configuration of the optical system of the zoom lens of Example 1 according to the first embodiment of the present invention and the short focal point, that is, the long focal point, that is, the telephoto end through a predetermined intermediate focal length from the wide angle end. FIG. 4A shows a zoom trajectory associated with zooming, wherein (a) is a cross-sectional view at the short focal end, that is, a wide-angle end, (b) is a cross-sectional view at a predetermined intermediate focal length, and (c) is a long focal end, It is sectional drawing in a telephoto end. In FIG. 1 showing the lens group arrangement of Example 1, the left side in the figure is the object (subject) side.
The zoom lens shown in FIG. 1 includes, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group having a positive refractive power. G3 is arranged. An aperture stop AD is disposed between the first lens group G1 and the second lens group G2.
The first lens group G1 includes, in order from the object side, a negative lens L11 having a concave surface on the image side, a negative lens L12 having a concave surface on the image side, a biconcave lens L13, and a positive lens L14 having a convex surface on the object side. The second lens group G2 includes a positive lens L21, a positive lens L22, a negative lens L23, a positive lens L24, a negative lens L25, and a positive lens L26, which are sequentially arranged from the object side. The third lens group G3 includes only a positive lens L31.

The first lens group G1 to the third lens group G3 are each supported by a common support frame or the like that is appropriate for each group, and operate integrally for each group during zooming or the like. Works independently. FIG. 1 also shows the surface numbers of the optical surfaces. 1 are used independently for each embodiment in order to avoid complication of explanation due to an increase in the number of digits of the reference code. Therefore, even if the same reference numerals as those in the drawings according to the other embodiments are attached, they are not necessarily the same configuration as the other embodiments.
When zooming from the short focal end (wide angle end) to the long focal end (telephoto end), the first lens group G1 to the third lens group G3 are moved, and the first lens group G1 and the second lens group are moved. The distance between the second lens group G2 and the third lens group G3 is changed so that the distance between the second lens group G2 and the third lens group G3 changes.
1 is a first embodiment according to the present invention, and the first lens group G1 of the zoom lens of Example 1 (numerical example, hereinafter the same) has a convex shape on the object side in order from the object side. A negative lens L11 composed of an aspherical lens that is a negative meniscus lens with the concave surface formed with a hybrid aspherical surface facing the image surface side, a convex shape on the object side, and an aspherical surface on the image side. A negative lens L12 composed of an aspherical lens that is a negative meniscus lens with a concave surface facing, a biconcave lens L13 with a concave surface having a larger curvature than the object side surface on the image side, and a curvature from the image side surface on the object side. A positive lens L14 is arranged from a biconvex lens having a large convex surface.

The aperture stop AD is interposed between the first lens group G1 and the second lens group G2.
The second lens group G2, in order from the object side, is a biconvex lens having a convex surface having a larger curvature than the image surface side toward the object side, and a positive lens L21 including an aspheric lens having aspheric surfaces on both surfaces; A positive lens L22 composed of a biconvex lens having a convex surface having a larger curvature than the image surface side, a negative lens L23 composed of a biconcave lens having a concave surface having a larger curvature than the object side surface, and an object side A positive lens L24 made of a positive meniscus lens having a convex surface, a negative lens L25 made of a biconcave lens having a concave surface having a larger curvature than the object-side surface on the image surface side, and a curvature of the image surface-side surface on the object side. A positive lens L26 which is a biconvex lens having a large convex surface and an aspheric lens having an aspheric surface on the image surface side is disposed.
Then, the three lenses of the second lens group G2, the positive lens L22, the negative lens L23, and the positive lens L24, are closely bonded to each other and integrally joined to form a cemented lens composed of three lenses. Yes. The two lenses of the second lens group G2, the negative lens L25 and the positive lens L26, are closely bonded to each other and are integrally joined to form a cemented lens composed of two lenses.

The third lens group G3 is a positive meniscus lens having a convex shape on the object side and a concave surface facing the image side, and is composed of only a single positive lens L31 having a hybrid aspheric surface on the image side. .
In this case, as shown in FIG. 1, the first lens group G1 moves from the object side to the image side with zooming from the short focal end (wide angle end) to the long focal end (telephoto end). The aperture stop AD moves slightly from the object side to the image side. The second lens group G2 moves from the image side to the object side. The third lens group G3 moves substantially monotonously from the image side to the object side.
In Example 1, the focal length f, the F number F, and the half angle of view ω of the entire optical system are f = 3.96 to 5.37 to 7.7 by zooming from the short focal end to the long focal end, respectively. 27, F = 1.85 to 2.16 to 2.51 and ω = 51.44 to 41.90 to 33.34. The optical characteristics of each optical element are as shown in Table 1 below.

In Table 1, the lens surface with the surface number indicated by adding “* (asterisk)” to the surface number is an aspherical surface. Table 1 also shows the material of each lens. The same applies to the other embodiments.
That is, in Table 1, the optical surfaces of the third surface, the fifth surface, the eleventh surface, the twelfth surface, the nineteenth surface, and the twenty-second surface marked with “*” are aspherical surfaces. The parameters of each aspheric surface in) are as shown in Table 2 below.

In the first embodiment, the focal length f, F value, half angle of view ω of the entire optical system, the variable distance DA between the first lens group G1 and the aperture stop AD, the aperture stop AD and the second lens group G2, The variable amount DB such as the variable distance DB between the second lens group G2 and the third lens group G3, the variable distance DD between the third lens group G3 and the filter FG, etc. As shown in Table 3, it changes as shown in Table 3 below.
Of the variable interval DA in the following table 3, the numerical value corresponding to Wide corresponds to TL1s_w in the conditional expression (6). Of the variable interval DB in the following table 3, the numerical value corresponding to Wide is This corresponds to TLs2_w in conditional expression (6).

  In this case, values corresponding to the conditional expressions (1) to (6) are as shown in the following table 4, which satisfy the conditional expressions (1) to (6), respectively.

  2, 3, and 4 respectively show spherical aberration, astigmatism, distortion, and lateral aberration at the short focal end (wide angle end), intermediate focal length, and long focal end (telephoto end) of Example 1. Each aberration diagram of the aberration is shown. In these aberration diagrams, the broken line in the spherical aberration diagram represents the sine condition, the solid line in the astigmatism diagram represents sagittal, and the broken line represents meridional. The same applies to the aberration diagrams of the other examples.

FIG. 5 shows the lens configuration of the optical system of the zoom lens of Example 2 according to the second embodiment of the present invention and the short focal point, that is, the long focal point, that is, the telephoto end after passing through a predetermined intermediate focal length from the wide angle end. FIG. 4A shows a zoom trajectory associated with zooming, wherein (a) is a cross-sectional view at the short focal end, that is, a wide-angle end, (b) is a cross-sectional view at a predetermined intermediate focal length, and (c) is a long focal end, It is sectional drawing in a telephoto end. In FIG. 5 showing the lens group arrangement of Example 2, the left side in the figure is the object (subject) side.
The zoom lens shown in FIG. 5 includes, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group having a positive refractive power. G3 is arranged. An aperture stop AD is disposed between the first lens group G1 and the second lens group G2.
The first lens group G1 includes, in order from the object side, a negative lens L11 having a concave surface on the image side, a negative lens L12 having a concave surface on the image side, a biconcave lens L13, and a positive lens L14 having a convex surface on the object side. The second lens group G2 includes a positive lens L21, a positive lens L22, a negative lens L23, a positive lens L24, a negative lens L25, and a positive lens L26, which are sequentially arranged from the object side. The third lens group G3 includes only a positive lens L31.

The first lens group G1 to the third lens group G3 are each supported by a common support frame or the like that is appropriate for each group, and operate integrally for each group during zooming or the like. Works independently. FIG. 5 also shows the surface numbers of the optical surfaces.
When zooming from the short focal end (wide angle end) to the long focal end (telephoto end), the first lens group G1 to the third lens group G3 are moved, and the first lens group G1 and the second lens group are moved. The distance between the second lens group G2 and the third lens group G3 is changed so that the distance between the second lens group G2 and the third lens group G3 changes.
FIG. 5 shows a second embodiment of the present invention, wherein the first lens group G1 of the zoom lens of Example 2 has a convex shape on the object side in order from the object side and forms a hybrid aspherical surface. A negative lens L11 made of an aspheric lens that is a negative meniscus lens with the concave surface facing the image surface side, a convex shape on the object side, an aspheric surface on both sides, and a concave surface on the image surface side. A negative lens L12 composed of an aspherical lens that is a negative meniscus lens facing the lens, a biconcave lens L13 having a concave surface having a larger curvature than the object side surface on the image side, and a positive meniscus lens having a convex surface directed to the object side. A positive lens L14 is disposed.

The aperture stop AD is interposed between the first lens group G1 and the second lens group G2.
The second lens group G2, in order from the object side, is a biconvex lens having a convex surface having a larger curvature than the image surface side toward the object side, and a positive lens L21 including an aspheric lens having aspheric surfaces on both surfaces; A positive lens L22 composed of a biconvex lens having a convex surface having a larger curvature than the image surface side, a negative lens L23 composed of a biconcave lens having a concave surface having a larger curvature than the object side surface, and an object side A positive lens L24 made of a positive meniscus lens having a convex surface, a negative lens L25 made of a negative meniscus lens having a concave surface facing the image surface side, and a biconvex lens having a convex surface having a curvature larger than that of the image surface side on the object side And a positive lens L26 made of an aspherical lens having an aspherical surface formed on the image plane side.
Then, the three lenses of the second lens group G2, the positive lens L22, the negative lens L23, and the positive lens L24, are closely bonded to each other and integrally joined to form a cemented lens composed of three lenses. Yes. The two lenses of the second lens group G2, the negative lens L25 and the positive lens L26, are closely bonded to each other and are integrally joined to form a cemented lens composed of two lenses.

The third lens group G3 is a positive meniscus lens having a convex shape on the object side and a concave surface facing the image side, and is composed of only a single positive lens L31 having a hybrid aspheric surface on the image side. .
In this case, as shown in FIG. 5, the first lens group G1 moves from the object side to the image side with zooming from the short focal end (wide angle end) to the long focal end (telephoto end). The aperture stop AD moves so as to draw a convex arc on the image plane side. The second lens group G2 moves from the image side to the object side. The third lens group G3 moves so as to draw a convex arc on the object side.
In Example 2, the focal length f, the F number F, and the half angle of view ω of the entire optical system are f = 4.63 to 8.32 to 14.3 by zooming from the short focal end to the long focal end, respectively. 96, F = 1.85 to 2.53 to 3.44 and ω = 47.03 to 29.76 to 17.70. The optical characteristics of each optical element are as shown in Table 5 below.

In Table 5, the lens surface with the surface number indicated by adding “* (asterisk)” to the surface number is an aspherical surface. Table 5 also shows the material of each lens. The same applies to the other embodiments.
That is, in Table 5, the optical surfaces of the third surface, the fourth surface, the fifth surface, the eleventh surface, the twelfth surface, the nineteenth surface, and the twenty-second surface marked with “*” are aspherical surfaces. The parameters of each aspheric surface in Equation (7) are as shown in Table 6 below.

In Example 2, the focal length f, the F value, the half angle of view ω of the entire optical system, the variable distance DA between the first lens group G1 and the aperture stop AD, the aperture stop AD and the second lens group G2, The variable amount DB such as the variable distance DB between the second lens group G2 and the third lens group G3, the variable distance DD between the third lens group G3 and the filter FG, etc. With this change, it changes as shown in Table 7 below.
Of the variable interval DA in the following table 7, the numerical value corresponding to Wide corresponds to TL1s_w in the conditional expression (6), and in the variable interval DB of the following table 7, the numerical value corresponding to Wide is This corresponds to TLs2_w in conditional expression (6).

  In this case, the values corresponding to the conditional expressions (1) to (6) are as shown in Table 8 below, which satisfy the conditional expressions (1) to (6), respectively.

  6, FIG. 7 and FIG. 8 respectively show spherical aberration, astigmatism, distortion, and lateral aberration at the short focal end (wide angle end), intermediate focal length and long focal end (telephoto end) of Example 2. Each aberration diagram of the aberration is shown. In these aberration diagrams, the broken line in the spherical aberration diagram represents the sine condition, the solid line in the astigmatism diagram represents sagittal, and the broken line represents meridional. The same applies to the aberration diagrams of the other examples.

FIG. 9 shows the lens configuration of the optical system of the zoom lens of Example 3 according to the third embodiment of the present invention, and the short focal point, that is, the long focal point, that is, the telephoto end through a predetermined intermediate focal length from the wide angle end. FIG. 4A shows a zoom trajectory associated with zooming, wherein (a) is a cross-sectional view at the short focal end, that is, a wide-angle end, (b) is a cross-sectional view at a predetermined intermediate focal length, and (c) is a long focal end, It is sectional drawing in a telephoto end. In FIG. 9 showing the lens group arrangement of the third embodiment, the left side in the figure is the object (subject) side.
The zoom lens shown in FIG. 9 includes, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group having a positive refractive power. G3 is arranged. An aperture stop AD is disposed between the first lens group G1 and the second lens group G2.
The first lens group G1 includes, in order from the object side, a negative lens L11 having a concave surface on the image side, a negative lens L12 having a concave surface on the image side, a biconcave lens L13, and a positive lens L14 having a convex surface on the object side. The second lens group G2 includes a positive lens L21, a positive lens L22, a negative lens L23, a positive lens L24, a negative lens L25, and a positive lens L26, which are sequentially arranged from the object side. The third lens group G3 includes only a positive lens L31.

The first lens group G1 to the third lens group G3 are each supported by a common support frame or the like that is appropriate for each group, and operate integrally for each group during zooming or the like. Works independently.
When zooming from the short focal end (wide angle end) to the long focal end (telephoto end), the first lens group G1 to the third lens group G3 are moved, and the first lens group G1 and the second lens group are moved. The distance between the second lens group G2 and the third lens group G3 is changed so that the distance between the second lens group G2 and the third lens group G3 changes.
In the third embodiment of the present invention shown in FIG. 9, the first lens group G1 of the zoom lens of Example 3 has, in order from the object side, a convex shape on the object side and a hybrid on the image surface side. A negative lens L11 composed of an aspheric lens that is a negative meniscus lens having a concave surface formed with an aspheric surface, and a negative meniscus having a convex shape on the object side and a concave surface formed with an aspheric surface on the image side A negative lens L12 made of an aspheric lens as a lens, a negative meniscus lens L13 with a concave surface facing the image side, and a positive meniscus lens with a convex surface facing the object side are arranged.

The aperture stop AD is interposed between the first lens group G1 and the second lens group G2.
The second lens group G2, in order from the object side, is a biconvex lens having a convex surface having a larger curvature than the image surface side toward the object side, and a positive lens L21 including an aspheric lens having aspheric surfaces on both surfaces; A positive lens L22 composed of a biconvex lens having a convex surface having a larger curvature than the image surface side, a negative lens L23 composed of a biconcave lens having a concave surface having a larger curvature than the object side surface, and an object side A positive lens L24 made of a positive meniscus lens having a convex surface, a negative lens L25 made of a negative meniscus lens having a concave surface facing the image surface side, and a biconvex lens having a convex surface having a curvature larger than that of the image surface side on the object side And a positive lens L26 made of an aspherical lens having an aspherical surface formed on the image plane side.
Then, the three lenses of the second lens group G2, the positive lens L22, the negative lens L23, and the positive lens L24, are closely bonded to each other and integrally joined to form a cemented lens composed of three lenses. Yes. The two lenses of the second lens group G2, the negative lens L25 and the positive lens L26, are closely bonded to each other and are integrally joined to form a cemented lens composed of two lenses.

The third lens group G3 is a positive meniscus lens having a convex shape on the object side and a concave surface facing the image side, and is composed of only a single positive lens L31 having a hybrid aspheric surface on the image side. .
In this case, as shown in FIG. 9, the first lens group G1 moves from the object side to the image side with zooming from the short focal end (wide angle end) to the long focal end (telephoto end). The aperture stop AD moves so as to draw a convex arc on the image plane side. The second lens group G2 moves from the image plane side to the object side. The third lens group G3 moves so as to draw a convex arc on the object side.
In Example 3, the focal length f, the F number F, and the half angle of view ω of the entire optical system are f = 4.63 to 8.32 to 14.3 by zooming from the short focal end to the long focal end, respectively. 95, F = 1.85 to 2.60 to 3.58 and ω = 47.54 to 29.95 to 17.65. The optical characteristics of each optical element are as shown in Table 9 below.

In Table 9, the lens surface with the surface number indicated by adding “* (asterisk)” to the surface number is an aspherical surface. Table 9 also shows the material of each lens. The same applies to the other embodiments.
That is, in Table 9, the optical surfaces of the third surface, the fifth surface, the eleventh surface, the twelfth surface, the nineteenth surface, and the twenty-second surface marked with “*” are aspheric surfaces, and the formula (7 Table 10 shows the parameters of each aspheric surface in ().

In Example 3, the focal length f, F value, half angle of view ω of the entire optical system, the variable distance DA between the first lens group G1 and the aperture stop AD, the aperture stop AD and the second lens group G2, The variable amount DB such as the variable distance DB between the second lens group G2 and the third lens group G3, the variable distance DD between the third lens group G3 and the filter FG, etc. As shown in the following Table 11, it changes.
Of the variable interval DA in the following table 11, the numerical value corresponding to Wide corresponds to TL1s_w in the conditional expression (6). Of the variable interval DB in the following table 11, the numerical value corresponding to Wide is This corresponds to TLs2_w in conditional expression (6).

  In this case, the values corresponding to the conditional expressions (1) to (6) are as shown in the following table 12, which respectively satisfy the conditional expressions (1) to (6).

  10, 11, and 12 show spherical aberration, astigmatism, distortion, and lateral aberration at the short focal end (wide angle end), intermediate focal length, and long focal end (telephoto end) of Example 3, respectively. Each aberration diagram of the aberration is shown. In these aberration diagrams, the broken line in the spherical aberration diagram represents the sine condition, the solid line in the astigmatism diagram represents sagittal, and the broken line represents meridional. The same applies to the aberration diagrams of the other examples.

FIG. 13 shows the lens configuration of the zoom lens optical system of Example 4 according to the fourth embodiment of the present invention and the short focal point, that is, the long focal point, that is, the telephoto end, after passing through a predetermined intermediate focal length from the wide angle end. FIG. 4A shows a zoom trajectory associated with zooming, wherein (a) is a cross-sectional view at the short focal end, that is, a wide-angle end, (b) is a cross-sectional view at a predetermined intermediate focal length, and (c) is a long focal end, It is sectional drawing in a telephoto end. In FIG. 13 showing the lens group arrangement of Example 4, the left side in the figure is the object (subject) side.
The zoom lens shown in FIG. 13 includes, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group having a positive refractive power. G3 is arranged. An aperture stop AD is disposed between the first lens group G1 and the second lens group G2.
The first lens group G1 includes, in order from the object side, a negative lens L11 having a concave surface on the image side, a negative lens L12 having a concave surface on the image side, a biconcave lens L13, and a positive lens L14 having a convex surface on the object side. The second lens group G2 includes a positive lens L21, a positive lens L22, a negative lens L23, a positive lens L24, a negative lens L25, and a positive lens L26, which are sequentially arranged from the object side. The third lens group G3 includes only a positive lens L31.

The first lens group G1 to the third lens group G3 are each supported by a common support frame or the like that is appropriate for each group, and operate integrally for each group during zooming or the like. Works independently.
When zooming from the short focal end (wide angle end) to the long focal end (telephoto end), the first lens group G1 to the third lens group G3 are moved, and the first lens group G1 and the second lens group are moved. The distance between the second lens group G2 and the third lens group G3 is changed so that the distance between the second lens group G2 and the third lens group G3 changes.
In the fourth embodiment of the present invention shown in FIG. 13, the first lens group G1 of the zoom lens of Example 4 has a convex shape on the object side and a hybrid on the image surface side in order from the object side. A negative lens L11 composed of an aspheric lens that is a negative meniscus lens having a concave surface formed with an aspheric surface, and a negative meniscus having a convex shape on the object side and a concave surface formed with an aspheric surface on the image side A negative lens L12 composed of an aspheric lens as a lens, a biconcave lens L13 having a concave surface having a larger curvature than the object side surface on the image side, and a biconvex lens having a convex surface having a larger curvature than the image side surface on the object side To a positive lens L14.

The aperture stop AD is interposed between the first lens group G1 and the second lens group G2.
The second lens group G2, in order from the object side, is a biconvex lens having a convex surface having a larger curvature than the image surface side toward the object side, and a positive lens L21 including an aspheric lens having aspheric surfaces on both surfaces; A positive lens L22 composed of a biconvex lens having a convex surface having a larger curvature than the image surface side, a negative lens L23 composed of a biconcave lens having a concave surface having a larger curvature than the object side surface, and an object side A positive lens L24 made of a positive meniscus lens having a convex surface, a negative lens L25 made of a biconcave lens having a concave surface having a larger curvature than the object-side surface on the image surface side, and a curvature of the image surface-side surface on the object side. A positive lens L26 which is a biconvex lens having a large convex surface and an aspheric lens having an aspheric surface on the image surface side is disposed.
Then, the three lenses of the second lens group G2, the positive lens L22, the negative lens L23, and the positive lens L24, are closely bonded to each other and integrally joined to form a cemented lens composed of three lenses. Yes. The two lenses of the second lens group G2, the negative lens L25 and the positive lens L26, are closely bonded to each other and are integrally joined to form a cemented lens composed of two lenses.

The third lens group G3 is a positive meniscus lens having a convex shape on the object side and a concave surface facing the image side, and is composed of only a single positive lens L31 having a hybrid aspheric surface on the image side. .
In this case, as shown in FIG. 13, the first lens group G1 moves from the object side to the image side with zooming from the short focal end (wide angle end) to the long focal end (telephoto end). The aperture stop AD moves so as to draw a convex shape on the object side. The second lens group G2 moves from the image side to the object side. The third lens group G3 moves substantially monotonously from the image side to the object side.
In Example 4, the focal length f, F number F, and half angle of view ω of the entire optical system are f = 3.96 to 5.37 to 7.7 by zooming from the short focal point to the long focal point, respectively. 27, F = 1.85 to 1.96 to 2.46 and ω = 51.44 to 41.91 to 33.23. The optical characteristics of each optical element are as shown in Table 13 below.

In Table 13, the lens surface with the surface number indicated by adding “* (asterisk)” to the surface number is an aspherical surface. Table 13 also shows the material of each lens. The same applies to the other embodiments.
That is, in Table 13, the optical surfaces of the third surface, the fifth surface, the eleventh surface, the twelfth surface, the nineteenth surface, and the twenty-second surface marked with “*” are aspherical surfaces. Table 14 shows the parameters of each aspheric surface in ().

In Example 4, the focal length f, F value, half angle of view ω of the entire optical system, the variable distance DA between the first lens group G1 and the aperture stop AD, the aperture stop AD and the second lens group G2, The variable amount DB such as the variable distance DB between the second lens group G2 and the third lens group G3, the variable distance DD between the third lens group G3 and the filter FG, etc. As shown in Table 15, it changes as follows.
The numerical value corresponding to Wide in the variable interval DA in the following table 15 corresponds to TL1s_w in the conditional expression (6), and the numerical value corresponding to Wide in the variable interval DB in the following table 15 is This corresponds to TLs2_w in conditional expression (6).

  In this case, the values corresponding to the conditional expressions (1) to (6) are as shown in Table 16 below, which satisfy the conditional expressions (1) to (6), respectively.

14, 15, and 16 show spherical aberration, astigmatism, distortion, and lateral aberration at the short focal end (wide angle end), intermediate focal length, and long focal end (telephoto end), respectively, in Example 4. Each aberration diagram of the aberration is shown. In these aberration diagrams, the broken line in the spherical aberration diagram represents the sine condition, the solid line in the astigmatism diagram represents sagittal, and the broken line represents meridional. The same applies to the aberration diagrams of the other examples.
In Examples 1 to 4 described above, the lens material is mainly glass. However, the lens of the third lens group may be a resin lens because the influence of the image quality due to surface accuracy is not great.

[Fifth Embodiment]
Next, the zoom lens according to the first embodiment to the fourth embodiment of the present invention described above, which employs a zoom lens such as the first to fourth embodiments as a photographing optical system, is configured. A camera according to a fifth embodiment will be described with reference to FIGS. FIG. 17 is a perspective view schematically showing an external configuration of a digital camera as a camera according to the fifth embodiment of the present invention viewed from the object side, and FIG. 18 is a view of the digital camera viewed from the photographer side. It is a perspective view which shows typically the outer appearance structure. FIG. 19 is a block diagram showing a functional configuration of the digital camera. Note that FIGS. 17 to 19 describe a digital camera as a camera, but not only an imaging device mainly dedicated to imaging including a video camera and a conventional film camera using a so-called silver film, It corresponds to a digital camera etc. in various information devices including portable terminal devices such as mobile phones, PDAs (personal data assistants) and so on, and so-called smart phones and tablet terminals including these functions. In many cases, an imaging function is incorporated.

Such an information device also includes substantially the same functions and configurations as those of a digital camera or the like, although the appearance is slightly different. Such an information device includes the first embodiment of the present invention described above. The zoom lens according to the fourth embodiment can be used as an imaging optical system.
As shown in FIGS. 17 and 18, the digital camera includes a camera body 100, an imaging lens (photographing lens) 101, an optical finder 102, a strobe (electronic flashlight) 103, a shutter button 104, a power switch 105, and a liquid crystal monitor 106. , An operation button 107, a memory card slot 108, a zoom switch 109, and the like. Further, as shown in FIG. 19, the digital camera includes a central processing unit (CPU) 111, an image processing device 112, a light receiving element 113, a signal processing device 114, a semiconductor memory 115, a communication card 116 and the like in a camera body 100. It has.
The digital camera includes an imaging lens 101 as an imaging optical system, and a light receiving element 113 configured as an image sensor using a CMOS (complementary metal oxide semiconductor) imaging element or a CCD (charge coupled device) imaging element. The light receiving element 113 reads a subject optical image formed by the imaging lens 101. As the imaging lens 101, the zoom lens according to the first to fourth embodiments of the present invention as described in the first to fourth embodiments is used.

The output of the light receiving element 113 is processed by a signal processing device 114 controlled by the central processing unit 111 and converted into digital image information. The image information digitized by the signal processing device 114 is recorded in a semiconductor memory 115 such as a nonvolatile memory after being subjected to predetermined image processing in the image processing device 112 which is also controlled by the central processing unit 111. In this case, the semiconductor memory 115 may be a memory card loaded in the memory card slot 108 or a semiconductor memory built on board in the digital camera body. The liquid crystal monitor 106 can display an image being shot, or can display an image recorded in the semiconductor memory 115. The image recorded in the semiconductor memory 115 is transmitted to the outside via a communication card 116 or the like loaded in a communication card slot (not shown explicitly, but may also be used as the memory card slot 108). Is also possible.
When the camera is carried, the objective surface of the imaging lens 101 is covered with a lens barrier (not clearly shown). When the user operates the power switch 105 to turn on the power, the lens barrier opens, The objective surface is exposed. At this time, in the lens barrel of the imaging lens 101, the optical systems of the respective groups constituting the zoom lens are arranged at, for example, a short focal end (wide angle end). The arrangement of the group optical system is changed, and the zooming operation to the long focal end (telephoto end) can be performed via the intermediate focal length.

It is desirable that the optical system of the optical viewfinder 102 is also scaled in conjunction with the change in the angle of view of the imaging lens 101.
In many cases, focusing is performed by half-pressing the shutter button 104.
Focusing in the zoom lens according to the first to fourth embodiments of the present invention (the zoom lens defined in claims 1 to 8 or shown in the examples 1 to 4 described above) is a zoom lens. Can be performed by moving a part of the plurality of groups of optical systems. When the shutter button 104 is further pushed down to the fully depressed state, photographing is performed, and then the processing as described above is performed.
When the image recorded in the semiconductor memory 115 is displayed on the liquid crystal monitor 106 or transmitted to the outside via the communication card 116 or the like, the operation button 107 is operated in a predetermined manner. The semiconductor memory 115 and the communication card 116 are used by being loaded into dedicated or general-purpose slots such as the memory card slot 108 and the communication card slot, respectively.
When the imaging lens 101 is in the retracted state, the groups of the imaging lenses do not necessarily have to be aligned on the optical axis. For example, if the mechanism is such that at least one of the second lens group G2 and the third lens group G3 is retracted from the optical axis and retracted in parallel with the other lens groups when retracted, the digital camera can be made thinner. Can be realized.

As described above, the imaging apparatus such as the digital camera (camera) described above or an information apparatus having a similar imaging function is similar to the first to fourth embodiments (Examples 1 to 4). An imaging lens 101 configured using a zoom lens can be used as an imaging optical system. Therefore, an image device such as a small digital camera with high image quality using a light receiving element with 10 to 20 million pixels or more is realized, or an information device such as a portable information terminal device having a similar image pickup function. be able to.
The configuration of the zoom lens according to the first to fourth embodiments of the present invention can also be applied as a photographing lens of a conventional silver salt film camera or a projection lens of a projector.

G1 first lens group (negative)
L11 Negative lens L12 Negative lens L13 Biconcave lens L14 Positive lens G2 Second lens group (positive)
L21 Positive lens L22 Positive lens L23 Negative lens L24 Positive lens L25 Negative lens L26 Positive lens G3 Third lens group (positive)
L31 Positive lens AD Aperture stop FG filter, etc. 100 Camera body 101 Imaging lens 102 Optical viewfinder 103 Strobe (electronic flashlight)
104 Shutter button 105 Power switch 106 Liquid crystal monitor 107 Operation button 108 Memory card slot 109 Zoom switch 111 Central processing unit (CPU)
112 Image processing device 113 Light receiving element (area sensor)
114 Signal processor 115 Semiconductor memory 116 Communication card, etc.

JP 2007-249087 A JP 2008-122875 A JP 2008-040159 A

Claims (10)

  In order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power are arranged from the short focal end. Along with zooming to the long focal end, the distance between the first lens group and the second lens group decreases and moves so that the distance between the second lens group and the third lens group changes. In the zoom lens, an aperture stop is disposed between the first lens group and the second lens group, and the first lens group has, in order from the object side, a negative lens L11 having a concave surface on the image side, and a concave surface on the image side. A negative lens L12, a biconcave lens L13, and a positive lens L14 having a convex surface on the object side, and the second lens group in order from the object side is a positive lens L21, a positive lens L22, and a negative lens. Lens L23, positive lens L24, and negative lens L25 , The zoom lens, characterized in that it consists of a positive lens L26. The focal length of the first lens group is f1, and the focal length of the entire optical system at the short focal end is fw.
Conditional formula (1) below:
−4.0 <f1 / fw <−3.0 (1)
The zoom lens according to claim 1, wherein: The focal length of the second lens group is f2, and the focal length of the entire optical system at the short focal end is fw.
Conditional formula (2) below:
3.0 <f2 / fw <5.0 (2)
.
The zoom lens according to claim 1, wherein the zoom lens satisfies the following. The focal length of the third lens group is f3, and the focal length of the entire optical system at the short focal end is fw.
Conditional expression (3) below:
6.0 <f3 / fw <16.0 (3)
The zoom lens according to claim 1, wherein the zoom lens satisfies the following.   5. The zoom lens according to claim 1, wherein the third lens group includes a single positive lens convex on the object side. The thickness of the first lens group on the optical axis is D1, and the focal length of the entire optical system at the short focal end is fw.
Conditional expression (4) below:
3.5 <D1 / fw <6.5 (4)
The zoom lens according to claim 1, wherein the zoom lens satisfies the following. The thickness on the optical axis of the second lens group is D2, and the focal length of the entire optical system at the short focal end is fw.
Conditional formula (5) below:
2.5 <D2 / fw <4.5 (5)
The zoom lens according to claim 1, wherein the zoom lens satisfies the following. The distance between the aperture stop and the second lens group at the short focus end is TLs2_w, and the distance between the first lens group and the aperture stop at the short focus end is TL1s_w.
Conditional formula (6) below:
0.10 <TLs2_w / TL1s_w <0.60 (6)
The zoom lens according to claim 1, wherein the zoom lens satisfies the following.   A camera comprising the zoom lens according to any one of claims 1 to 8 as a photographing optical system.   A portable information terminal device having a photographing function and comprising the zoom lens according to claim 1.

Images